- Synthesis and characterization of oligo- and crown ether-substituted polythiophenes - A comparative study
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The synthesis of two series of thiophenes substituted with crown and oligoether groups either via isolating oxaalkyl chains (2, 7-11) or in direct π-conjugation (4, 12-15) is described. Electrooxidative polymerization leads to the corresponding crown and oligoether-functionalized polythiophenes P2, P7-P11, and P4, P12, respectively. Their electrochemical and spectroscopic properties depend on the length of the spacer and the type of the ether unit. The polymers reveal a high mean conjugation. A specific and strong influence of alkali ions on the electrochemical behavior is found for several polymers. The selectivities correspond to the match of the cation size without solvent shell and the inner diameter of the crown ether units. Spectroelectrochemical experiments corroborate that the changes in redox properties are due to a hindered diffusion of the counter anions into the film when the polymer is oxidized. Due to the structural variation novel materials sensitive to different cations are obtained. Importantly, in these conjugated polymers chemical information which corresponds to a selective host-guest interaction of the alkali metal cations and the ether units is transduced into the change of an electrical signal.
- Scheib, Stefan,Baeuerle, Peter
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- Design and synthesis of novel electroactive 2,2′:5′,2″-terthiophene monomers including oxyethylene chains for solid-state flexible energy storage applications
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Here, we present the synthesis of novel poly(2,2′:5′,2″-terthiophene) derivatives containing oxyethylene pendant groups for the fabrication of high performance flexible redox-active electrode materials. The poly(3′,4′-bis(2-methoxyethoxy)-2,2′:5′,2″-terthiophene) (PSEDEN1), poly(3′,4′-bis(2-(2-methoxyethoxy)ethoxy)-2,2′:5′,2″-terthiophene) (PSEDEN2) and poly(3′,4′-bis(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)-2,2′:5′,2″-terthiophene) (PSEDEN3) have been electrochemically polymerized on flexible stainless steel substrates without any binder and directly employed as redox-active materials. The effect of pendant group chain length on morphological characteristics of conducting polymer films have been systematically evaluated and correlated to the charge storage properties of redox-active electrode materials. Capacitive performance tests reveal that PSEDEN1, PSEDEN2 and PSEDEN3 could reach up to specific capacitances of 135 F g?1, 212.8 F g?1 and 403.3 F g?1, respectively, at constant current density of 2.5 mA cm?2 in the potential range of 0.4–1.8 V with good rate capability performances. In addition, symmetrical flexible solid-state supercapacitor devices based on polymer gel electrolyte have also been assembled using PSEDEN1, PSEDEN2 and PSEDEN3 coated flexible stainless steel substrates and tested by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy techniques in detail. Fabricated devices (Cell 1, Cell 2 and Cell 3) have delivered maximum specific capacitances of Cspec= 29.3 F g?1, 92.1 F g?1 and 162.4 F g?1, energy densities of SE= 6.35 W h kg?1, 22.9 W h kg?1 and 41.1 W h kg?1 and power densities of SP= 929 W kg?1, 937.7 W kg?1 and 986.4 W kg?1 at a current density of 2.5 mA cm?2 in two-electrode cell configuration. Furthermore, flexible supercapacitor devices have achieved high cycle life performances with good capacitance retention values of 80.2%, 84.7% and 91.4% over 10 000 consecutive galvanic charge/discharge cycles at 2.5 mA cm?2 constant current density from 0.4 to 1.8 V. Similarly, excellent mechanical stabilities have also been observed with 3.4%, 4.66% and 1.97% capacitance losses under various bending conditions from 0° to 170° for all flexible supercapacitor devices. These results confirm that PSEDEN1, PSEDEN2 and PSEDEN3 redox-active materials with gratifying capacitive performances and excellent flexibilities have a great potential for utilization in innovative flexible or wearable energy storage solutions. Keywords
- Güllü, Mustafa,Yi?it, Deniz
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